DESCRIPTION: The goal is to establish a reliable, easy means of determining exposure (biomarkers) to wood smoke for use in larger field and epidemiological studies. During inversion episodes in the late fall and winter of the year, these cresols will be evaluated in first morning urine voids because they are rapidly eliminated from the body. These data will be compared to baselines collected in a non-wood burning season. Questionnaire data will serve to identify potential subject confounders (e.g., diet).